Mathematics and General Physics. 359 



ed to in the constructing of public buildings, in which lec- 

 tures, sermons, or other discourses, were intended to be deli- 

 vered. He drew the attention of the Section to two distinct 

 cases, first, where, as in a church, the speaker is, for the most 

 part, placed in one fixed place ; second, where, as in the Houses 

 of Lords and of Commons, the speakers require to be heard from 

 many various quarters. The author then gave some remarkable 

 instances of the great distances at which sounds had been heard ; 

 one of the most curious of which instances was, that when the 

 fleet engaged, we believe, in the blockade of Copenhagen, were 

 in a very extended line, ships at the one end distinctly heard, 

 and recorded in their logs, a loud cannonade, which they heard 

 on a particular day ; and it was found afterwards, by a compa- 

 rison of the logs of the ships, that this very cannonade pro- 

 ceeded from the proving of large pieces of ordnance, which had 

 been conducted for the greater part of a day at a dockyard in 

 the neighbourhood of one end of the fleet, from which the other 

 end, at which the reports were heard, was distant three hundred 

 miles. He also mentioned several well authenticated cases, where 

 the human voice had been heard distinctly at a distance of be- 

 tween one and two miles, and stated, that in numerous experi- 

 ments made in the open air, under every variety of circum- 

 stances, in the neighbourhood of Edinburgh, in which he was 

 assisted by a number of different individuals, they found no dif- 

 ficulty, when the atmosphere was still, of carrying on a conver- 

 sation at distances varying from 200 to 1000 feet. Dr Reid 

 concluded, accordingly, that where there is any difficulty in the 

 communication of sound in large buildings, this must arise ge- 

 nerally, not so much from any want of power in the voice of the 

 speaker, as from a prolonged reverberation maintained between 

 the walls, or between the floor and the roof, and wherever this was 

 observedj there would be no deficiency of sound, or rather noise, 

 but a great want of all purity of tone or distinctness of articula- 

 tion. He then shewed how the reverberating of sound from 

 the ceiling, walls, and floor of a room, by being continued too 

 long, and interfering with each other, would have the effect of 

 producing a confusing noise, and thus interfering with the hear- 

 ing of the succeeding parts of the discourse. From all the pre- 

 mises which he had previously laid down, he concluded, that 



